Solventless silicone compositions are used as release liners of adhesive tapes and sheets for forming, cured films with an ability to release from adhesive substances. When these release films are peeled with low speed (below approximately 0.3 m/min), resistance to peeling is allowed in a wide range from low to high. However, when peeling is carried out with a high speed (50 m/min or higher), it is required that resistance to peeling be relatively low. Japanese Patent Application No. 2-187466 discloses a solventless silicone release coating composition prepared from an polyorganohydrogensiloxane, a platinum catalyst, and a mixture of polydiorganosiloxanes comprising a copolymer of dimethylsiloxane and methylvinylsiloxane and a copolymer of diphenylsiloxane, methylvinylsiloxane, and dimethylsiloxane with diphenylsiloxane units in an amount of 0.5 to 3.0 mole %. A drawback of this composition is high resistance to peeling and a decrease in residual adhesion of the adhesive material that has been applied onto the cured release film. For these reasons, the above composition was not always satisfactory in use. In Japanese Patent Application Nos. 9-125004, 10-158519, and 2-145649, is disclosed a composition comprising an uncured copolymer of methylhexenylsiloxane and dimethylsiloxane having both molecular terminals capped with trimethylsiloxy groups, a polyorganohydrogensiloxane, a platinum catalyst, and an organic solvent. Since the main component of this composition is a polydiorganosiloxane having hexenyl groups and comprising a rubber-like high-molecular-weight substance, it is required that the composition be diluted in an organic solvent. llowever, organic solvents not only are harmful to the health of the workers who work with such solvents, but also are costly since they require the use of various means to prevent evaporation of these solvents into the surrounding atmosphere. In addition, the use of the cured films produced from the aforementioned compositions is not always satisfactory. This is because, when peeling is carried out at high speed (exceeding approximately 50 m/min), it is difficult to ensure low resistance to peeling.
In Japanese Patent Application No. 7-258606 it was proposed to utilize solventless silicone release coating composition having a main component in the form of polyorganosiloxane having both molecular terminals capped with trialkylsiloxy groups and with two or more vinyl groups in a side chain. In Japanese Patent Publication 62-86061 was disclosed a silicone release coating composition having as its main component a polydiorganosiloxane having alkenyl groups containing 6 or more carbon atoms in one molecule. Although the aforementioned compositions are free of problems associated with the use of organic solvents and are not subject to decrease in the coefficient of residual adhesion in the adhesive material applied onto the cured release films, they still have high resistance to peeling when peeling is performed at a high speed (approximately 50 m/min or higher).